Apparatus for correcting nonuniformity in a rotating tire

ABSTRACT

The method and apparatus for reducing the radial force variation of a rotating tire by grinding from the tread a portion thereof as determined by the radial motion of a floating load wheel which provides an electrical signal proportional to the movement of the load wheel axis. The electrical signal is employed in a circuit such that when a reference voltage is exceeded, the signal is effective to move a grinder to and away from contact with the tire tread in increments of constant radial depth but of varying time duration. The apparatus comprises a tire uniformity machine having a pulse generator synchronized with the tire rotation so each pulse indicates a unit angle of tire rotation. A comparator conducts the pulses only when the signal from the uniformity machine exceeds a predetermined value such that the pulses activate alternately a pair of one-shot multivibrators which energize actuating solenoids for applying or retracting the grinder. The solenoids move a bell crank which causes a snapaction toggle to advance or retract the grinder with respect to the tire tread.

United States Patent Shively et al.

[ 1 APPARATUS FOR CORRECTING NON- UNIFORMITY IN A ROTATING TIRE [72]Inventors: Harmon G. Shively, Tallmadge; Clifford A. Akron, both of Ohio[73] Assignee: The B. F. Goodrich Company, New

York, N.Y.

[22] Filed: Aug. 12, 1969 [21] Appl. No.: 849,340

[52] US. Cl ..51/106 R, 51/1659, 51/281,

51/324, 157/13 [51] Int. Cl. ..B24b 5/00 [58] FieldotSearch ..51/165 R,106 R; 73/146 [56] References Cited UNITED STATES PATENTS 2,695,52011/1954 Karsai ..73/146 2,766,563 10/1956 Bennett ..51/33 X 2,966,01 112/1960 Beacock ..5 [[33 3,500,681 3/1970 Shively ..73/146 3,553,903l/l97l Christie ..51/106 R X 3,574,973 4/1971 Rader ..5 H1659 FOREIGNPATENTS OR APPLICATIONS 1,177,328 1/1970 Great Britain...........5l/l65R [4s] Aug. 8, 1972 Primary Examiner-[ester M. Swingle Attorney-W. A.Shira, Jr. and Harold S. Meyer ABSTRACT The method and apparatus forreducing the radial force variation of a rotating tire by grinding fromthe tread a portion thereof as determined by the radial motion of afloating load wheel which provides an electrical signal proportional tothe movement of the load wheel axis. The electrical signal is employedin a circuit such that when a reference voltage is exceeded, the signalis effective to move a grinder to and away from contact with the tiretread in increments of constant radial depth but of varying timeduration. The apparatus comprises a tire uniformity machine having apulse generator synchronized with the tire rotation so each pulseindicates a unit angle of tire rotation. A comparator conducm the pulsesonly when the signal from the uniformity machine exceeds a predeterminedvalue such that the pulses activate alternately a pair of one-shotmultivibrators which energize actuating solenoids for applying orretracting the grinder. The solenoids move a bell crank which causes asnap-action toggle to advance or retract the grinder with respect to thetire tread.

9 Claims, 5 Drawing Figures PATENTEDAUE 8 I972 3.681. 8 7 7 'JI'EXTOR. S

- HARMQN C. SHIVELY O CLIFFORD A. Lmwsusss BY AT Tf.

27a 271 g T 5 wrEx'T i/RS F G, a HARMON G. SHIVELY CI FORD A.LANDSNESSPATENTEDAUB 8 m2 3,681,877

SHEET 36? 4 f J SENSOR f/ja W 14 {AMPLIFIER PULSE ONE PULSE/DEG.

GATE j5 REFERENCE 16 VOLTAGE PULSER COMPARATOR /8 l7 AMPLIFIER T nnnnn ne DELAY NJRlND" SHIFT RCEGISTER) 19 20 AMPLIFIER -21 POWER SUPPLYTRIGGER -22 23 FIG.4CL

3O MiLLI SEC. INTEGRATlNG DELAY m Q1235? START T No GRIND" nunnnm. t

'WEYTQRS HAR MON 6. SHWELY CLIFFORD A. LANDSNESS I, l "l 'QA'I'TY.

PATENTEDAUB 61912 3681877 I24 -25 ONE SHOT ONE SHOT MULTI-VIBRATORMULTl-VIBRATOR (oEcAvING (RISING VOLTAGE) VOLTAGE) 3O MILL| SOMILLI- fF- -fi I sEc.-I

T i I ig START No GRIND" 2 "GRIND" C3OMlLLl SEQDELAY 29w 3 3oMII I I-SEC.DELAY No-GRIND" GRIND" SOLENOID SOLENOID BELL CRANK FIG. 49:

GRINDER E/G INVENTOR S I I? i 'r 1 A, AT T X.

APPARATUS FOR CORRECTING NON- UNIFORMITY IN A ROTATING TIRE BACKGROUNDOF THE INVENTION It is essential that pneumatic tires for vehicles, suchas passenger automobiles, exert a minimum force variation on the axlewhile running under load in order to prevent undesirable oscillations ofthe vehicle suspension. Therefore, the dynamic variation in the forcesradially applied to the axle while the tire is rotating must be kept toa minimum in order to produce this result. When the allowable limits ofradial force variation of the completed tire are exceeded, the tire isgenerally unusable for passenger car service. This requires that thepneumatic tires be manufactured or corrected to maintain withinpredetermined limits the eccentricity or radial runout, carcassflex-stiffness and lateral oscillation. One method of reducing theradial force variation of a completed tire is that of buffing orgrinding rubber from the tread region of the tire, preferably from theaxial edges thereof.

In the manufacture of pneumatic tires, one common means of determiningthe radial force variation of a completed tire is that of testing thetire on a uniformity machine." In this type machine, the tire is mountedon a rim and in the inflated state is rotated at a nearly constantspeed. A movable load wheel is urged into contact with the tread of thetire while it is rotating. The load wheel has sensors, usuallyelectrical transducers, attached to its shaft, or axle mounting, suchthat motion of the load wheel is detected in a direction radial to thetire and an electrical signal varying proportionally to the load wheelmovement is provided. The varying voltage of the electrical signalcorresponds to the variation in radial force of the tire tread againstthe load wheel since the movement of the load wheel is directlyproportional to the variations in radial force exerted by the tire onthe load wheel.

in order to reduce the radial force variation by removing material fromthe tread region while the tire is rotating on a uniformity machine, itis necessary to apply the varying electrical signal from the load wheeltransducers to a controlling and actuating mechanism for operating thematerial remover which may be a buffer, or grinder, as the case may be.A convenient technique of providing grinder or bufier operation has beento drive the grinder at a fixed rotational speed and alternately movethe grinding wheel into contact with the tire tread and then away fromthe tread.

Heretofore, in order to control the amount of material removed from thetire tread region by the grinder, attempts have been made to control theradial depth of penetration of the grinder in the tire tread by makingthe radial movement of the grinder proportional to the voltage of theelectrical signal emanating from the load wheel transducers. This typeof grinder control is often called a linear system in view of theattempts to make the grinder movement directly proportional to themagnitude of voltage of the continuously varying electrical signal.

In practice, the linear type of grinder control is extremely difficultto achieve in order to remove enough material from the tire tread at theproper peripheral location on the tire when the tire is rotating at evenmodest speeds. The problem is due primarily to the difficulty in movingthe large mass of the grinder alternately radially inwardly andoutwardly at sufiicient speed to provide the required grinderresponsiveness to the variation in the electrical signal voltage at thefrequency produced by the tire rotational speed. This difficulty hasserved to render an otherwise useful method of salvaging defective tiresimpractical in view of the complexity and cost of machinery necessary toprovide adequate grinder response movement.

Heretofore, a grinder capable of removing material rapidly enough toenable grinding at typical tire uniformity test rotation speedsexhibited such a large mass that the actuators and controls, forproviding the force required to move the grinder quickly enough to grindonly at the proper tire location, did not have sufficient sensitivity torespond to the frequency of the signal from the load wheel sensors.Thus, the method of grinding tire treads to reduce variation in tireradial force to acceptable limits for use in passenger vehicleproduction has required grinding equipment of great complexity andprohibitive cost.

SUMMARY OF THE INVENTION The present invention provides a solution tothe problem of removing material from the tread region of a rotatingtire by moving the grinder radially into and away from contact with thetire tread in increments of constant radial depth but of varying timeduration. The varying electrical signal from the load wheel sensors of auniformity testing apparatus is compared with a fixed reference voltagelevel representing the maximum allowable variation in radial force andis conducted only when the voltage exceeds the reference level. A seriesof equal electrical pulses, each representing a unit angle of tirerotation is provided by a generator on the rotating tire axle and thesepulses are permitted to be conducted only when the signal from the loadwheel sensors exceeds the reference level. The pulses are applied to apair of single pulse generators which alternately energize actuators formoving a grinder either into contact or away from the tire tread. Theactuators are interconnected to a snap-action, spring loaded togglewhich is set close to the trip point such that only a small force fromeither actuator is required to trip the toggle which moves the grinder afixed radial distance either into contact with or away from the tiretread.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of atire uniformity machine incorporating the present invention in itspreferred embodiment;

FIG. 2 is a plan view of the grinder and actuator portion of FIG. 1;

FIG. 3 is a portion of a sectional view taken along the sectionindicating lines 33 of FIG. 2; and

FIG. 4a and 4b, when placed in vertical alignment, comprise a block flowdiagram of the control circuit for operating the grinder.

DETAILED DESCRIPTION Referring now to FIG. 1, a tire uniformity machineM is shown in side view having a tire T mounted therein on a verticallydisposed axle arrangement which, in the usual practice, comprises twomovable rotatable chuck plates 10a and 10b such that the tire may bemounted inflated and rotated about a vertical shaft 10. A load wheel Wis positioned such that it may be moved radially into contact with thetread of the tire. The load wheel is supported by bearings 12 at theends of the vertical shaft and the bearings are resiliently mounted onflex plates 1 1 such that the load wheel can move in its plane ofrotation in a direction perpendicular to its axle 10. Sensors lla aremounted on the flex plates 11 for determining the motion of the loadwheel axle. In the preferred practice of the invention, the sensors 11acomprise electrical transducers which provide a varying electricalsignal with the magnitude of the voltage signal directly proportional tothe radial displacement of the load wheel axle 10'. The tire T isrotated by a power means P connected to its axle 10 and mounting chucks10a and 10b of the tire.

The load wheel and its axle 10' and bearing assembly are mounted on amovable carriage C which is slidably mounted on rails R to urge the loadwheel W into contact with the tire tread. The load wheel is shown in theretracted position in FIG. 1 with the surface of the wheel notcontacting the tire tread. A threaded power nut N is engaged with athreaded jack screw S attached to the carriage C and the threaded nut isrotated by a motor and transmission assembly P. Rotation of the nut Ncauses the load wheel to be brought to and from contact with the tiretread. The arrangement of the tire uniformity machine in FIG. 1 may beessentially as described in a co-pending application assigned to theassignee of the present invention and entitled AP- PARATUS FOR LOCATINGMAXIMUM RADIAL FORCE VARIATION IN A TIRE, Ser. No. 751,969, filed Aug.12, 1968, now US. Pat. No. 3,500,681, dated Mar. 17, 1970, in whichapplication is disclosed and claimed the machine and its operation forproviding an electrical signal for indicating force variation in thetire.

Referring now to FIGS. 2 and 3, the detail of the grinder mechanism areshown enlarged from FIG. 1 such that the description thereof may be moreclearly understood. The grinder G is rotatably mounted on a lever 40intermediate the ends thereof and a second lever 41 has one endpivotally attached to lever 40 at the point where the grinder G ismounted thereon. Levers 40 and 41 intersect and are pivotally attachedsuch that each may be moved with respect to the other with the grinder Gbeing free to rotate and unaffected in its rotation by the scissor-likemovement of either lever 40 or 41.

One end of the lever 40 has a register means 42 attached thereto formaking contact with the tire tread. Similarly the lever 41 has a portion41a intermediate the ends thereof which portion has a second registermeans 43 attached thereto for making running contact with the tiretread. In the preferred form of the invention, the register means 42 and43 comprises a pair of spaced idler rollers rotatably mountedrespectively to levers 40 and 41. The rollers 42 and 43 are spacedclosely adjacent on opposite sides of the grinder with the axis ofrotation of each idler parallel to that of the grinder. In operation,scissoring the levers 40 and 41 moves the idlers toward or away fromeach other, thereby advancing or retracting the grinder G radially withrespect to its position in relation to the tire tread. Levers 40 and 41are scissored such that when the idler rollers 42 and 43 are advancedtoward the center of the rotating tire: the grinder G is thus retractedfrom grind position. When the levers 40 and 41 are scissored such thatthe idlers 42 and 43 are retracted away from the center of the tire, thegrinder G is advanced toward and urged into contact with the tire treadfor removing material therefrom.

The grinder and actuator assembly is supported by an elongated bar 44,see FIG. 2, having one end 4411 pivotally attached to the intersectionof lever-arms 40 and 41 and the other end of the bar 44 pivotallyattached to a frame means 45 at a pivot mount 45a provided thereon forconnecting to the said bar. The frame means comprises a portion of theframe of the machine shown in FIG. 1. The bar 44 has a mounting portion44c intermediate the ends thereof with a clevis 46 pivotally attachedthereto, which clevis is interconnected to an actuator 47 having oneoperative portion thereof pivotally connected to a second mountingportion 45b spaced from the pivot mount portion 45a on said frame. Inthe preferred practice of the invention, the actuator 47 comprises apneumatic or hydraulic power cylinder with one end connected to clevis46 and the other end pivotally attached to the frame 45. In operationpower cylinder 47 operates to rotate the arm 44 about the first mountportion 450 of the frame such that the entire grinder assembly is movedtoward or away from the rotating tire. The power cylinder 47 is operatedto urge the grinder and idler rollers 42 and 43 into contact with thetire tread, it being determined by the scissored position of the levers40 and 41 with respect to each other whether or not the grinder contactsthe tire. However, the idler rollers 42 and 43 are preferably positionedsuch that initially the rollers engage the tire tread, the grinder Gremaining spaced from the tire tread.

A pulley 48 is provided on the shaft of the grinder G and is operativelyinterconnected by means of a driving belt 49 to a power means 50 rigidlyattached to frame 45. In the presently preferred practice, power means50 is a motor having its shaft of rotation axially coincident with thecenter of pivot of the end 440 of the bar 44. This permits the arm 44 tobe rotated about its pivotal attachment to the frame without changingthe distance between the pulley 48 and the shaft of the motor, thusmaintaining constant tension in the drive belt 49 in all positions ofthe arm 44.

The free end of the lever 40 has a clevis 40a attached thereon. The freeend of the lever 41 has a fork 41' rigidly formed therein with the armsof the fork extending from the lever 41 in spaced mutually parallelarrangement with each arm of fork 41' parallel to the length of the arm41. The bell crank 30 having rigidly mounted intermediate its ends arigid pivot shaft 30a extending perpendicularly from the bell crank. Theends 30b of the shaft are rotatably mounted between the arms of the fork41 such that the pivot shaft 30a is parallel to the axis of rotation ofthe grinder. The bell crank 30 also has a portion 30c, see FIG. 3,extending therefrom, which portion has one end of a linkage bar 52pivotally attached thereto and the other end of the linkage barpivotally attached to the clevis 40a on the end of the arm member 40. Inoperation, rotation of the bell crank about its shaft 30a causes thelinkage bar 52 to operate as a toggle for scissoring the ends of the armmembers 40 and 41 with respect to each other. As described above, thismovement then causes the idler rollers 42 and 43 to move together orfurther apart, thereby extending or retracting the grinder respectivelyaway from or towards the center of the tire.

A U-shaped bracket 53, having each of its open ends adjustably attachedto'one end respectively of the fork 41', see FIGS. 2 and 3, has mountedin the closed portion thereof actuator means 26 and 27 for rotating thebell crank. As described above with reference to FIG. 4a and 4b, theactuator means comprise respectively a pair of electrical solenoids 26and 27. Each solenoid has respectively an armature 26a and 27a extendingtherefrom with each armature having respectively a clevis 26b and 27battached to the end thereof. The clevis 26b is attached to one arm ofthe bell crank 30 such that, upon electrical energizing, the solenoid 26causes the armature 26a to retract, thereby rotating the bell crank in adirection such that the bar 52 causes lever-arms 40 and 41 to scissorwith respect to each other in a manner spreading the idler rollers 42and 43 further apart and permitting the grinder G to contact the tire.The clevis 27b is pivotally attached to an arm of the bell crank on theopposite side of the pivot shaft 30a from the clevis 26b. In operation,electrical actuation of solenoid 27 causes the armature 27a to retract,thus rotating the bell crank 30 in a direction such that the linkage 52scissors lever arm members 40 and 41 in a manner converging idlerrollers 42 and 43 toward each other thereby retracting the grinder Gfrom material removing position.

Thus, the grinder G is advanced toward or retracted away frommaterial-removing, or grinding, position by alternate actuation of thesolenoids 26 and 27. The limitations of the actuating stroke of thesolenoids thus determine the limit of radial travel of the grinder. Thegrinder thus operates in a succession of predetermined fixed radialmovements toward or away from the tire, with each movement providing thesame depth of penetration of the grinder into the tire tread as theprevious movement.

A snap-action means indicated by arrow F in FIG. 2 and FIG. 3 isprovided to assist the toggle action of the bell crank 30 and thelinkage bar 52 such that in the retracted or no grind" position, thesnap-action mechanism F is near the trip point. A small amount ofmovement of the armature 26a of the grind" solenoid causes thesnap-action mechanism F to go over center and provide a continuing forceassist to movement of the bell crank 30. In the grind" position thesnap-action means is near the trip point for the return stroke such thata small amount of movement of the armature 27a of the no grind" solenoid27 causes the snap-action means to throw over center and give forceassistance to the retracting stroke of the bell crank 30.

In the preferred form of the invention, the snap-action means Fcomprises a generally 1r-shaped frame 54 having the open ends of thesides thereof adjustably attached to the sides of bracket 53. Aconnecting bar 55 extends through the pivotal connection between thelinkage bar 52 and the arm 30b of the bell crank and also extendsthrough clearance holes 530 formed one in each side of the bracket 53such that movement of the bell crank causes the bar 55 to move laterallywithin the clearance holes 530. A pair of coil springs 56 and 57 isprovided with the end of one spring attached each to one end of the bar55 and the opposite end of the coil spring anchored to an extension ofthe closed end of the bracket 54. The springs are disposed such thatsnap-action occurs about a line through the pivot center of the bellcrank passing through the end of the coil spring anchored to the bracket54. The springs are thus positioned in mutually parallel arrangement andprovide a snap-action of the bell crank 30 about its pivot axis. Anadjustment means 58 is provided at the attachment of the bracket 54 tothe bracket 53 such that the position of the coil springs may be changedfor effecting a snap-action pivoting of the bell crank at a difi'erentposition in its rotation. In the preferred form of the invention, theadjustment is provided by a slot 54a in each side of bracket 54 and athreaded bolt 58 attached respectively to each side of the bracket 53.The bracket 54 is pivotally mounted about the pivot center of the bellcrank and it is attached to bracket 53 such that the attachment bolts 58may be loosened and bracket 54 pivoted about the bell crank pivot centerand the bolts 58 then tightened to secure the new position of thebracket 54 with respect to bracket 53 thus permitting variation in thesnap position of the bell crank.

A further adjustment in the mechanism is provided by a sleeve nut 52aattached to the linkage bar 52 such that the bar may be lengthened orshortened by rotation of the sleeve nut. This permits changes in therelative positions of the arms 40 and 41 with respect to each other suchthat the idler wheels 42 and 43 may be adjusted with respect to thegrinder G.

In operation, the power cylinder 47 is actuated by an independent sourceto move arm 44 to bring the idler rollers 42 and 43 into running contactwith the rotating tire T when it is desired to begin thematerial-removing cycle. The motor 50 may then be started to bring thegrinder wheel G to the desired rotational speed.

Referring now to FIG. 4a and 4b, a schematic flow diagram is shown inwhich the signal from the sensors is fed to amplifier l4 and then to apulse-gate 15. A pulse generating means, or pulser, 16 (see also FIG. 1)is driven by the tire axle 10 such that rotation of the tire mountedthereon causes the pulse generator to transmit equal pulses with eachpulse representing a unit angle of tire rotation. In the preferredpractice of the invention, the pulse generator 16, or pulser, as it islabeled in FIG. 4a, has an output signal of one pulse per degree of tirerotation, which output is applied to the input of the pulse-gate. Thepulser 16 may be of any convenient commercial type. In the presentpractice of the invention, a Rotaswitch Pulser, Model No. 815- P343l,manufactured by the Disc Instrument Company, has been used, but anyother commercially available unit may be employed. Similarly, thepulsegate 15 may be of any standard construction or type known in theart and it may be of semi-conductor or vacuum-tube design. Operation ofthe pulse-gate 15 is such that the signals from the amplifier 14 are nottransmitted by the pulse-gate unless the pulse-gate 15 is receivingpulses from the generator 16.

The signals passed from the pulse-gate 15 are then applied to acomparator amplifier 18 which receives also a voltage from a referencesource 17. The comparator amplifier 18 operates as a summing amplifiersuch that the pulses are transmitted to its output only when the voltagesignal from the sensors exceeds the level from the reference source 17.The reference voltage is a predetermined value to represent the maximumallowable limit of radial force variation which is permissible in thetire. When the signal from the sensors exceeds this level in magnitude,the pulses from the generator 16 are transmitted and used to initiatethe grinder operation.

Signals from the comparator amplifier 18 are applied to the input of adelay means 19 which serves to delay the signal an amount in tirerotation time represented by the angular distance the tire must rotatefor a point under the load wheel to pass under a grinder G. This angulardistance is represented in the upper right-hand portion of FIG. 40 bythe Greek letter Theta 6. The grinder G is located at a convenientposition around the tire and delay means 19 is used to synchronizeoperation of the grinder with passage of the point associated with ahigh radial force value, such that the grinder G does not operate untilthe point passes in rotation directly beneath the grinder.

The delay means 19 preferably comprises a static shift register whichmay be of conventional design known in the art and may be of vacuum-tubeor semiconductor design or may employ relays. In the presently preferredpractice the shift register is a Motorola static eight-bit shiftregister, Model MC845P. The pulse signals from the shift register areapplied to a second amplifier 20 and subsequently applied to anelectrical trigger 22 which is supplied power from the power supply 21.The trigger 22 serves to apply sufficient power to means for moving thegrinder toward and away from the tire tread. The trigger 22 may be ofany conventional construction known in the electrical art. In thepreferred practice of the invention, a silicon control rectifier (SCR)firing circuit is employed with the signal from amplifier 20 applied tothe gate junction of the SCR. The signal from the trigger is thenapplied to the grinder moving means through an intermediate integratingdelay 23 and simultaneous application to a pair of intermediate singlepulse generators 24 and 25.

The integrating delay 23 is preferably a 30 millisecond delay to preventactivation of either multivibrator upon receipt of a series of pulsesignals of a duration less than 30 milliseconds. However, any convenienttime value may be used for the delay 23, the choice being governed bythe mechanical time response of the grinder mechanism in moving towardand away from the tire tread. The single pulse generators 24 and 25 arepreferably one-shot multi-vibrators with the generator 24 operating onlyupon excitation by the decaying voltage portion of the pulse signal, thegenerator 25 being energized only upon receipt of the rising voltageportion of the pulse signal. The output of the multivibrator 24 isapplied to an actuator 27 which retracts the grinder G from contact withthe tire tread and the output of multivibrator 25 is applied to anactuator 26 which moves the grinder G to contact the tire tread. In thepresently preferred practice of the invention, the actuators 26 and 27each comprise an electrical solenoid having an armature therein with oneend of each armature connected to bell crank 30 which in turn isconnected to the grinder G.

In operation, when a signal from the multivibrator 25 is received, bythe rising voltage of the first pulse in each group of pulses applied tothe multivibrator, the solenoid 26 is activated, which causes the bellcrank to move the grinder into material-grinding position. As the groupof pulse passes, application of the decaying voltage portion of the lastpulse in the group to multivibrator 24 causes the solenoid 27 to beactivated, which in turn rotates the bell crank in the oppositedirection, thereby retracting the grinder from materialgrindingposition.

The design of each of the multivibrators 24 and 25 is such that thepulse width of the output signal is greater than the time response ofthe grinder activating mechanism to prevent signals, which have a timeduration less than the response capability of the solenoid activatingdevice, from being applied to the solenoid. lt will be readily apparentthat such an arrangement is necessary to prevent chatter of the solenoidactuating mechanism.

The output of multivibrator 25 is also applied to a 30 millisecond delay28 and the output thereof is fed back into the input of thedecaying-voltage sensitive multivibrator 24. Similarly, the output ofmultivibrator 24 is applied also to a 30 millisecond delay 29 the outputof which is fed back into the input of the multivibrator 25. Thisarrangement provides a cross-coupled delay feedback of the multivibratoroutputs and in operation serves to prevent either multivibrator fromactivating for a period of time equal to the pulse width of the outputof the multivibrators.

In FIG. 4b, the multivibrator 25 and solenoid 26 which cause the grinderto move into contact with the tire are labeled as a grind" function andthe multivibrator 24 and solenoid 27 for retracting the grinder frommaterial grinding position are labeled as the no grind" function.Referring, in FIG. 4b, to the electrical output of comparator amplifier18, the maximum voltage of the pulse signals therefrom represents agrind signal and the zero voltage level between pulse groups representsthe no gring portion of the signal. With respect to the signal appliedto the input of the multivibrators, the rising voltage side of the pulsegroup represents the start grind function and the decaying voltage sideof the pulse group represents the start n0- grind" function.

Upon receipt of electrical pulse signal from the oneshot multivibrator25 the grind" solenoid 26 is actuated to rotate the bell crank, therebyscissoring lever arms 40 and 41 such that the idler rollers 42,43 aremoved farther apart and the rotating grinder G is moved a predetermineddistance into contact with the tire tread for removing material in thetread region. When an electrical pulse signal is received from theone-shot multivibrator 24 by the no-grind" solenoid 26, the armature ofthe solenoid is actuated to rotate the bell crank 30 in a direction suchthe lever arms 40,41 are scissored and the idler rollers 42,43 are movedcloser together thereby retracting the grinder G from material removingposition. Thus, alternate actuation of the grind" solenoid 26 and the nogrind solenoid 26 and the no grin solenoid 27 provides movement of therotating grinder G a predetermined distance into and away from thematerial-removing position. Springs 56 and 57 provide a snap-actionforce assist to rotation of the bell crank. Upon completion of thegrinding cycle, e.g., when the magnitude of signals from sensor 11a areno longer in excess of the reference voltage for the predeterminedminimum time duration, the power cylinder 47 is actuated to pivot arm 44and move the grinder assembly out of materialremoving position, in adirection radially outward of the tire, such that the idler rollers nolonger run against the rotating tire.

The operation of the present invention thus provides for separateactuators for moving the grinder a predetermined and fixed distance intocontact with, and away from, the tire tread upon receipt of a grind" ora no grind signal to the respective actuators. This technique is incontrast to one commonly known system wherein attempts have been made tomechanically actuate the grinders to move a distance into contact andaway from the tire directly proportional to the continuing variation inthe voltage from the radial force measuring sensors. The grinder in thepresent invention thus is urged into contact with the tire, grinds for atime determined by the pulse width of an electrical grind" signal andthen is retracted from the grind position until receipt of another grindsignal.

Modifications and adaptations of the invention may be made by thosehaving ordinary skill in the art with the invention being moreparticularly defined by the following claims.

We claim:

1. An apparatus for reducing the magnitude of radial force variation ina pneumatic tire comprising:

a. means for supporting and rotating the tire in inflated conditionabout its axis;

b. means responsive to radial force variation in the rotating tire toprovide an electrical signal the amplitude and duration of which isindicative of such force variation;

c. means supported adjacent the tire for movement a predetermineddistance to and from engagement therewith which means is capable ofremoving a portion of the tire tread when in engagement with the tire;

d. means for providing a reference voltage representative of a minimumlevel of said radial force variation;

. means responsive to the onset of that portion of said signal in excessof a said reference voltage for initiating movement of saidmaterial-removing means into engagement with the tire;

f. means responsive to the recession of said signal below said referencevoltage to withdraw said material-removing means from contact with thetire; and

. means attached to said material-removing means having a portionadapted to contact said tire to provide a reference base for themovement of the said material-removing means.

2. The apparatus defined in claim I, wherein said material-removingmeans includes means for effecting a snap-action of saidmaterial-removing means into and away from contact with the tire tread.

3. The apparatus as defined in claim 1, wherein a. the saidmaterial-removing means is spaced peripherally a distance along the tiretread from 'd m s to rovide e si nal; and, b. ih e sai m s respori ive oonset of the portion of said signal in excess of the reference voltageincludes means to delay actuation of said materialremoving means anamount in tire rotation time corresponding to the said distance betweensaid means to provide the signal and said materialremoving means.

4. The apparatus defined in claim 1, wherein said means responsive tothe onset and said means responsive to the recession of said portion ofsaid signal in excess of said reference voltage includes:

a. electrical pulse generating means emitting a series of equal durationdirect current pulses which pulses are synchronized with rotation ofsaid tire such that each pulse represents a unit angle of tire rotation;

b. electrical pulse gate means electrically connected to receive saidelectrical signal and said direct current pulses, the said pulse gatemeans being operative to pass said electrical signal only when saidpulses are received from said pulse generating means; and

. electrical comparator means electrically connected to the output ofsaid pulse gate means and to said reference voltage with the comparatoroperative to conduct said pulses only when said electrical signalexceeds said reference voltage.

5. The apparatus defined in claim 1, wherein said means adjacent thetire for movement a predetermined distance to and from engagementtherewith comprises:

a. a frame means;

b. a grinder;

0. means pivotally attaching said grinder to said frame; and,

d. actuator means operatively connected to the lastmentioned means foreffecting movement of said grinder toward and away from said tire.

6. The apparatus defined in claim 5, wherein said pivotal meansincludes:

a. toggle means operative to move said grinder radially relative to andfrom contact with the tire; and

b. a pair of electrical solenoids each having an annature pivotallyconnected to said toggle means for alternate operation of the latter toeffect said movement of the grinder respectively toward and away fromsaid tire.

7. The apparatus defined in claim 6, wherein said toggle means hasspring means attached thereto for effecting snap-action of said grinderin its movement to and from engagement with the tire.

8. The apparatus defined in claim 1, wherein said means attached to saidgrinder includes a pair of spaced rollers supported on said toggle meanswith the rollers individually disposed on opposite sides of saidgrinder.

9. The apparatus as defined in claim 1, further comprising means foradjusting the position of said grinder relative to said reference baseto thereby alter the extent of radial movement of the grinder relativeto the tire.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 77Dated August a 97 Inventor(s) Harmon G. ShiveJ X and Clifford A.Lendsness It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

In the references cited, "Beacock" should read ---Peacock---. Column 8,line 42, "no ring" should read ---no grind---.

Cglkumn 8, lines 63 and 4;, delete "and the no grind aolenoid 2 Signedand sealed this 10th day of April 1973.

(SEAL) Attest:

EDWARD 1 I.FLETCI-IER,JR. ROBERT G OTTSCHALK Attesting OfficerCommissioner of Patents

1. An apparatus for reducing the magnitude of radial force variation ina pneumatic tire comprising: a. means for supporting and rotating thetire in inflated condition about its axis; b. means responsive to radialforce variation in the rotating tire to provide an electrical signal theamplitude and duration of which is indicative of such force variation;c. means supported adjacent the tire for movement a predetermineddistance to and from engagement therewith which means is capable ofremoving a portion of the tire tread when in engagement with the tire;d. means for providing a reference voltage representative of a minimumlevel of said radial force variation; e. means responsive to the onsetof that portion of said signal in excess of a said reference voltage forinitiating movement of said material-removing means into engagement withthe tire; f. means responsive to the recession of said signal below saidreference voltage to withdraw said material-removing means from contactwith the tire; and g. means attached to said material-removing meanshaving a portion adapted to contact said tire to provide a referencebase for the movement of The said material-removing means.
 2. Theapparatus defined in claim 1, wherein said material-removing meansincludes means for effecting a snap-action of said material-removingmeans into and away from contact with the tire tread.
 3. The apparatusas defined in claim 1, wherein a. the said material-removing means isspaced peripherally a distance along the tire tread from said means toprovide the signal; and, b. the said means responsive to onset of theportion of said signal in excess of the reference voltage includes meansto delay actuation of said material-removing means an amount in tirerotation time corresponding to the said distance between said means toprovide the signal and said material-removing means.
 4. The apparatusdefined in claim 1, wherein said means responsive to the onset and saidmeans responsive to the recession of said portion of said signal inexcess of said reference voltage includes: a. electrical pulsegenerating means emitting a series of equal duration direct currentpulses which pulses are synchronized with rotation of said tire suchthat each pulse represents a unit angle of tire rotation; b. electricalpulse gate means electrically connected to receive said electricalsignal and said direct current pulses, the said pulse gate means beingoperative to pass said electrical signal only when said pulses arereceived from said pulse generating means; and c. electrical comparatormeans electrically connected to the output of said pulse gate means andto said reference voltage with the comparator operative to conduct saidpulses only when said electrical signal exceeds said reference voltage.5. The apparatus defined in claim 1, wherein said means adjacent thetire for movement a predetermined distance to and from engagementtherewith comprises: a. a frame means; b. a grinder; c. means pivotallyattaching said grinder to said frame; and, d. actuator means operativelyconnected to the last-mentioned means for effecting movement of saidgrinder toward and away from said tire.
 6. The apparatus defined inclaim 5, wherein said pivotal means includes: a. toggle means operativeto move said grinder radially relative to and from contact with thetire; and b. a pair of electrical solenoids each having an armaturepivotally connected to said toggle means for alternate operation of thelatter to effect said movement of the grinder respectively toward andaway from said tire.
 7. The apparatus defined in claim 6, wherein saidtoggle means has spring means attached thereto for effecting snap-actionof said grinder in its movement to and from engagement with the tire. 8.The apparatus defined in claim 1, wherein said means attached to saidgrinder includes a pair of spaced rollers supported on said toggle meanswith the rollers individually disposed on opposite sides of saidgrinder.
 9. The apparatus as defined in claim 1, further comprisingmeans for adjusting the position of said grinder relative to saidreference base to thereby alter the extent of radial movement of thegrinder relative to the tire.